Exposure to radiation from radioactive sources can be very dangerous to humans and some radioactive materials can be used in the creation of devastating weapons. It would be very desirable to have means for detection of such radiation in many environments, such as laboratories, nuclear power stations, transportation corridors, airports, train stations, and any area where large groups of people may gather.
Radioactive sources produce ionizing radiation when a single atom decays into another form. This ionizing radiation can come in several forms of high-energy particles including beta particles (which are high-energy electrons), alpha particles (which are helium nuclei) and gamma photons (which are high-energy photons). The beta and alpha particles may be stopped fairly quickly when they travel through material, but gamma photons can travel long distances before being absorbed.
Different isotopes produce different types of ionizing radiation and different energies of the radiation. For example, Cs-137 produces 662 keV photons. As another example, Co-60 produces 1173 and 1332 keV photons.
In contrast, ordinary light in the visible and near-visible ranges is non-ionizing and has much lower energies that are in the eV range. For example, at the low range of visible light photons for red light have about 1.77 eV of energy and at the high range of visible light photons for violet light have about 3.10 eV of energy.
Many portable devices such as digital cameras, cellular telephones, and tablets are becoming near ubiquitous as they become more portable and interconnected. In most cases, these portable devices include semiconductor image sensors for capturing visible light images and can be easily interfaced with a variety of communication networks. While not intended, these semiconductor imagers can absorb energy from high-energy particles that interact with the semiconductor image sensor and produce what appear to be artifacts on the image when capturing a visible light image.
The inventor has appreciated that there is a need for devices that are economical and readily available for detecting and reporting the presence of high-energy particles that indicate a radiation source is in the vicinity of the device.